Innate Spellcasting. Demogorgon's spellcasting ability is Charisma (spell save DC 24). Demogorgon can innately cast the following spells, requiring no material components:
Legendary Resistance (4/Day). If Demogorgon fails a saving throw, he can choose to succeed instead. Demonic Awakening (Recharges after a Short or Long Rest). If Demogorgon would be reduced to 0 hit points, his current hit point total instead resets to 373 (80% of his maximum hit points) hit points, he regains any expended uses of Legendary Resistance and he can use 2 more legendary actions per round. Additionally, he can now use the options in the "Mythic Actions" section for 1 hour. Magic Resistance. Demogorgon has advantage on saving throws against spells and other magical effects. Magic Weapons. Demogorgon's weapon attacks are magical. Two Heads. Demogorgon has advantage on saving throws against being blinded, deafened, stunned, or knocked unconscious.
Multiattack. Demogorgon makes two Tentacle attacks. He can replace one attack with a use of Gaze. Tentacle. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 28 (3d12 + 9) bludgeoning damage. If the target is a creature, it must succeed on a DC 24 Constitution saving throw, or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if its hit point maximum is reduced to 0. Gaze. Demogorgon turns his magical gaze toward one creature he can see within 120 feet of him. The target must succeed on a DC 24 Wisdom saving throw. Unless the target is incapacitated, it can avert its eyes to avoid the gaze and to automatically succeed on the save. If the target does so, it can't see Demogorgon until the start of his next turn. If the target looks at him in the meantime, it must immediately make the save. If the target fails the save, the target suffers one of the following effects (choose one or roll a d6): 1-2: Beguiling Gaze. The target is stunned until the start of Demogorgon's next turn or until Demogorgon is no longer within line of sight. 3-4: Insanity Gaze. The target suffers the effect of the confusion spell without making a saving throw. The effect lasts until the start of Demogorgon's next turn. Demogorgon doesn't need to concentrate on the spell. 5-6: Hypnotic Gaze. The target is charmed by Demogorgon until the start of Demogorgon's next turn. Demogorgon chooses how the charmed target uses its action, reaction, and movement. Because this requires Demogorgon to focus both heads on the target, he can't use his Maddening Gaze legendary action or Hypnotic Gaze Mythic Action until the start of his next turn.
Mislead. Demogorgon creates an illusory duplicate of himself, which appears in his own space and lasts until the start of his next turn. On his turn, Demogorgon can move the illusory duplicate a distance equal to his walking speed (no action required). The first time a creature or object interacts physically with Demogorgon (for example, hitting him with an attack), there is a 50 percent chance that it is the illusory duplicate that is being affected, not Demogorgon himself, in which case the illusion disappears. Hypnotic Pattern. Demogorgon casts the hypnotic pattern spell at its lowest level. Demogorgon doesn't need to concentrate on the spell, which ends at the end of his next turn.
Demogorgon can take 2 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Demogorgon regains spent legendary actions at the start of his turn. Tail. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) bludgeoning damage plus 11 (2d10) necrotic damage. Maddening Gaze. Demogorgon uses his Gaze action and must choose either the Beguiling Gaze or Insanity Gaze effect. Cast a Spell (Costs 2 Actions). Demogorgon casts a spell other than Silvery Barbs.
On Initiative count 20 (losing initiative ties), Demogorgon can take a lair action to cause one of the following effects: Demogorgon can't use the same effect two rounds in a row:
Demogorgon's lair is the palace Abysm.